38 FAULTS. 



tually prizes out masses of rock. In our special case, 

 however, it also acts on the soft lower beds (sand and 

 marl), and either carries them away, as may be seen 

 in the springs flowing out of the sand beds, or makes 

 them so soft and slippery that the superincumbent 

 mass has no foundation, and its connection behind 

 being already cut off by the joints, it must slide out- 

 ward. If joint-lines are perpendicular to an escarp- 

 ment, the action is quite different, as all drainage 

 takes place along these lines, and excavates ravines 

 with abrupt hills between ; and if these joints are near 

 together, the results of weathering in chalk will be 

 the carving out of " pillars," " needles," and such 

 like. Such a weathering does not, however, prove that 

 the escarpment is due to meteoric abrasion, as marine 

 action may work very similarly on joint-lines per- 

 pendicular to it. 



Of landslips in Mount Sirban, India, Wynne thus 

 writes : " The Nummulitic formation, as usual among 

 the border hills of the Punjab, is chiefly composed of 

 massive gray and blackish limestone, here alternating 

 with thick zones of dark-coloured shale. Its thick- 

 ness is very great, its stratification violently contorted, 

 and it possesses the same features, commonly ob- 

 servable, of profound gorges and ravines excavated 

 in it, high cliffs formed, and, upon slopes, of great 

 masses having subsided so as to produce complications 



